1. Field of the Invention.
This invention relates to a structure and method of verifying the registration of various layers of a multi-layer substrate. More particularly, this invention relates to a misregistration fidutial structure and method for verifying registration of an underlying conductive layer as seen through an aperture in an overlaying soldermask layer in a multi-layered electronic device.
2. Discussion of Related Technology.
Previously, to verify registration, or alignment, between two layers on a multi-layered electronic device subassembly, the subassembly had to be examined under a high power microscope. The feature sizes then had to be compared against a specification to determine proper registration of the layers with respect to each other. Such a method presents distinct disadvantages.
Another common method of verifying registration requires that a cross-section of the device be taken for examination.
It is desirable that visual observation of misregistration between the layers through an aperture be available at one or more locations on an electronic package subassembly. This type of fidutial would assure that any misalignment between a soldermask layer and an underlying conductive layer can be easily observed without requiring the use of a high power microscope, or that a cross-section of the subassembly be made and examined.